Question

Which one of the following is used in the whitewashing of walls?

• A. Calcium oxide mixed with water
• B. Calcium carbonate mixed with water
• C. Cadmium sulfate mixed with water
• D. Sodium chloride mixed with water

Answer 1

The correct option is A

Calcium oxide mixed with water

Calcium oxide is commonly known as quicklime. The whitewashing of walls is done using Calcium oxide (CaO) and water.

REASON: It reacts with water and produces Calcium hydroxide ($\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$).

$\mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to \mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)$

The calcium hydroxide formed undergoes a reaction with water (H₂O) and absorbs Carbon dioxide (CO₂) from the environment.

It produces a hard white coating on walls. This is due to the formation of Calcium carbonate .

Thus, option A is correct.

So, Calcium oxide mixed with water is used in the whitewashing of walls.